Microwave radiation has been used to heat a wide variety of materials to the point where temperatures are sufficient to create sterilization effects. Many materials, especially those which have not absorbed moisture, may require prolonged exposure at high power levels to ensure complete sterilization.
However, the determination of when a material is rendered inactive or destroyed by irradiation with microwaves still relies largely upon observable changes of the irradiated material. This reliance upon observation of the irradiated material may be impractical when the irradiated material is divided among a large number of discrete containers or when the irradiated material is a biological pathogen or toxic chemical, or may be unlawful for example in the case of opening the United States mail to obtain samples of the irradiated material.
Moreover, conventional irradiation devices and irradiation methods suffer from a lack of precision. Conventional material irradiation devices and methods rely upon a fixed frequency microwave source which provides a high intensity, non-specific radiation field that may be many times stronger than is required to sterilize or heat a particular material because determination as to when a material has been rendered inactive remains largely a matter of guesswork in many cases.
As to these problems and other problems related with conventional microwave irradiation of materials for the purpose of sterilization or heating of a material, rendering the material inactive or destroying the material, the instant invention addresses each in practical fashion.